Over the last 5 years, plasmid profile analysis has become an accepted epidemiological tool used to characterize different strains of the same organism. The technique is particularly useful since it appears to be broadly applicable to many different groups of organisms. The first group of organisms we will be looking at are coagulase-negative staphylococci (CONS). All hospitals, including the Clinical Center, have noted a significant increase in the number of CONS associated with infection. Because this organism is also a frequent contaminant, it is often difficult to assess a particular isolate's significance, to identify relapse versus reinfection, or to identify infections in different patients caused by the same strain. Plasmid profile analysis may be useful in these instances. Our preliminary work thus far suggests that by using a mini-gel agarose system, we can develop a one-day screening system. Once all the technical aspects of the procedure are defined, we intend to start screening blood and body fluid isolates of CONS to see how many different profile patterns are present, and their relative prevalence. A study is also underway of CONS from IV catheter tips and Port-a-cath culture isolates.